TIG Coolant investigation (long)

Hello All,

I been a TIG hobbyist for about 7 years, when I bought my Miller 180SD Syncrowave new. Through the years I've occasionally come up against both the high and low limits of the machine, and have always dreamed of finding a used 250 Syncro on the cheap.

Well, I found a non-working 350 Syncro of 1990 vintage for cheap, brought it home, cleaned it up, eventually found the problem (about $2 worth of components on PC1; a shorted tantalum cap that took out a couple of resistors and a PCB trace). Fan was noisy, put new bearings in the motor.

It now runs like a champ. Looks nice, welds nice. Plus it has the built-in pulser option, so I'm pretty happy now. My 180SD has been a great unit, but it's time for it to go to a new home.....

My largest torch today is a 17 aircooled, so I'm planning to get both

18 and 20 watercooled torches. Over the weekend, I found a good used Miller Coolmate 3 for sale and brought it home.

So I started researching the whole coolant issue on this NG and other forums. I wasn't aware when I bought the Coolmate of the pricey Miller low-conductivity coolant ($30 a gallon! and I need 3 gals for the Coolmate!)

So I started researching the various options. To sum up what I've found, some folks just hook up to flowing tap water, some use distilled water with their coolers if their keeping the unit in a warm shop, some use the pink RV Propylene Glycol stuff, some use ordinary auto antifreeze.(ethylene glycol mixes)

Obviously, Miller thinks that low conductivity is important. And it would seem to me that if your coolant is conductive, then you will lose strength of the HF. I have found no data on relative conductivity of various solutions, so tonight I rigged up a "kitchen experiment", pretty non-scientific from an absolute sense, but pretty good from a relative sense to check relative conductivity of various solutions.

I went to Wally World today and picked up a gallon of Distilled Water, a gallon of Prestone RV antifreeze, a gallon of Dow pink Dowfrost RV antifreeze. I already had a gallon of Zerex auto antifreeze and a few quarts of Pentosin Pink antifreeze in the garage.

I made a simple conductivity divider with a set of known resistances, and used 240VAC as the excitation voltage. (yes; I know that the high voltage of the HF output can have different conductivity characteristcs, but I wasn't going to mess with any higher voltage)

I constructed a simple conductivity cell with a glass beaker and a couple of stainless steel butter knives from the kitchen. (to keep with the "kitchen experiment" theme, of course)

I then used my Fluke 179 DMM to measure the voltage across the cell with various liquids in the cell. A pefect insulator would measure

240 VAC (actually 236 VAC according to my meter), a dead short would be 0 VAC. I rinsed out the beaker with distilled water between liquids.

Here's my findings:

Distilled Water: 42 VAC Hard well tap water : 700 millivolts AC Soft well tap water: 600 millivolts AC Prestone RV antifreeze: 115 millivolts AC Dow RV antifreeze: 175 millivolts AC Pentosin/Distilled 50%: 600 millivolts AC Zerex/distilled 50%: 550 millivolts AC

I investigated the theoretical conductivities of industrial ethylene and propylene glycol aqueous mixtures, and both should be in the range of near distilled water; around 5 micromhos/cm. I also found data that the Dow RV stuff has a conductivity about 2,000 micromhos/cm, or

400 times that of distilled water. This is close to what I observed. Obviously, both the RV and auto additives make the mixtures dramatically more conductive than the base water and glycol mixes. I've seen several assumptions in this NG that Miller doesn't recommend auto antifreeze because of stop leak additives. I think they don't recommend it because the damn stuff is so conductive....

Conclusions? Obviously distilled water is the way to go, but what about if you need freeze protection? (my shop isn't heated full time; rarely gets below freezing, but has a few times in the past) I would NEVER use the pink RV stuff of any brand. It is basically a dead short path for the HF back to your cooler. Tap water is much better, (my tap water, anyway. YMMV) Automotive stuff is marginally better. None of these are any good, really (IMHO.)

Here's my plan. I need 3 gallons for my system. The Miller low conductivity stuff would set me back $90. I have found several sources for both Propylene and Ethylene Glycol (industrial grade) for about $30 a gallon. I can easily get by with a 33% mixture for my shop, which will cost about $32 total, a $60 savings.

Here's a question to those running either tap water or especially pink RV stuff: Have you noticed a degradation of HF power, from conduction losses? Given my observations, it appears to me that you should. (Or perhaps suffer poor component life in your welder's HF circuitry?)



Reply to
Jeff W
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Congrats. What were the symptoms when you bought it?

A lot of people use pink RV antifreeze with no ill effects.

I use the pink RV stuff.

I think that you need very little strength to begin with, and pink RV antifreeze is not impeding it for me.

I noticed no ill effects, with hte pink stuff, HF is so strong at the highest setting that my dick would fall off if I set it that high.

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I have the older Lincoln cooler 10 (3 piston diaphragm) and use distilled water. The manual says to add alcohol or glycol to the mixture for sub- freezing temps. It specifically warns of using oil based coolants sold for other coolers (does not specify whether Esab or Miller).

Folks used city water for years, no problems except when you forgot to turn it on...

With the tanks using antifreeze the only thing I have noticed is that a sludge will build up in the tank. I'm not sure if it's due to bio activity or a reaction with the copper parts.

I've only refilled the cooler once in 10 years, (kinked the power cable, "POOF"). I replaced the cable, drained the system (water was clean except for some small white specs), and got back to going.

As an aside, Lincoln has replaced the piston pump (lower pressure high volume) with vane pumps (higher pressure lower cost) and raised the price of the cooler... I bought a spare pump (probably look good on my sale rack some day).


Reply to
matthew maguire

Unit would power up, fan running, displays light up with zeros, but no output. Previous owner had it diagnosed at a Miller authorized shop; was told that it had a bad PC1, which was true, however it also blew out a small resistor on the terminal block at the top of the machine. Simply replacing the board wouldn't have totally fixed it.

The PO didn't want to pay the Miller shop $ 1,000 for a new control board, but knew of places that would fix them for a couple hundred or so. He was concerned that if he had the board fixed on the cheap, that it wouldn't solve the problem, which proved to be true. He just ended up buying a new welder. His shop welded light gauge aluminum stuff; nothing heavy, so he bought a smaller unit. (a 250DX)

Before I had time to troubleshoot it, I came across a "new" control board for this exact machine on eBay and bought it for $ 90, just in case my board had unrepairable parts. (these boards have two output transformers that are special, and there is no replacement for them) the board turned out to be not new (it had been repaired at some point; obviously was a spare) but I put it in my machine after I fixed my board and it checks out fine. I now have a spare for my machine.

I used to work as an Engineering Technician for a small electronic scale manufacturer, and enjoy troubleshooting stuff like this. Miller has excellent documentation, and is very willing to help out. Not many companies out there like that anymore.

LOL, I don't think I'll do that experiment........

Reply to
Jeff W

I admire the work that you have done with this welder. Congratulations!

I fixed a Miller XMT once, but all that was wrong with it is a broken display current vs. voltage elector switch.


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